The present invention relates to a pipe coupling for plain-end relatively rigid pipes, and more specifically to such a pipe coupling which permits the adjacent pipe ends to be assembled with the coupling merely by inserting the pipe ends into the coupling. The pipe coupling must firmly grip the pipe ends to resist any tendency of the pipe ends to separate.
Pipe couplings of the type described are known wherein reverse biased continuous filament strands are embedded within coupling so that the strands will tighten and compress around the ends of a pipe if there is any tendency of the pipe ends to separate.
The coupling must resist not only tendency of the pipe ends to separate in an axial direction, but must also resist separation of the pipe ends radially from each other, that is, that the pipe coupling must resist in shear the tendency of the pipe ends to move out of axial alignment. It was found that the pipe coupling described above would develop leaks in a plane at right angles in either direction relative to the line of shear force. It is believed that due to the low elongation properties of the continuous filament strands customarily used, this mechanical action was upsetting the seal at the point of leak-field end terminating at right angles away and in line with the shear load.
Accordingly, it is an object of the present invention to provide a new and improved pipe coupling.
It is an object of the present invention to provide a new and improved coupling which overcomes the above-mentioned difficulties.
In accordance with the present invention there is provided a pipe coupling for plain-end relatively rigid pipe provided with relatively soft, spaced outer gripping zones and an inner zone of hard, tough material. Preferably the spaced outer gripping zones have embedded therein cross biased continuous filament strands and the inner zone is reinforced with discontinuous filament strands embedded therein.
Further features will appear hereinafter.